What the hell is going to run into hundreds - catch a grip!
I could clean the pee off the rug, right now, and you'd never know it had been peed on. £3.25 a bottle. Stop being so bloody dramatic!!
I haven't been to survey the house myself, so I couldn't tell you; but you're really minimising how much damage a trapped cat can do. It's not even just the rug - although we don't know how damaged it was - but the floorboards, the walls, the paintwork. If there's any furniture there, then I'll bet the cat gave it a really good scratch as well, as cats are normally wont to do.
As I said, I'm not talking about the costs to patch it up and make do, I'm talking about a proper professional job to repair the damage and restore everything to its original condition.
Like when renters vacate a property in a real state and the landlord withholds some/all of their deposit to pay for professional cleaning, repainting, repairs etc. - they don't just say "No worries - I'll give up my weekend and pop over there to do it all myself." Even paint isn't cheap - and the whole wall(s) may need to be repainted, as it tends to look awful if you just dab over the bits with marks on at a later date.